The Shore Crawler is a trainable pet in Mists of Pandaria. However, only Goblins are offered this option from Battle Pet Trainers. Once learned, all characters will have access to this pet. Goblins may also learn this pet from Varzok in Orgrimar.

NOTE: Once this pet is learned, it cannot be learned again from the trainer even if the pet is caged and sold.

There has been a bug with both the worgen and Pandaren pets, with new characters being unable to train the pet because they were unable to obtain 'Pet Training'. Not sure if Goblins have the same problem, but I would assume so. However, ticketing a GM and explaining the situation let me get the Pandaren's companion 'trained' to me. Therefore, if you're being bitten by this bug, opening a ticket is probably your best chance until Blizzard fixes this bug.